There are many presently known panoramic viewing optical arrangements which use lenses, or optical blocks, of various shapes. Examples of such arrangements are described in U.S. Pat. No. 3,552,820 to Brachvogel; U.S. Pat. No. 4,395,093 to Rosendahl et al; U.S. Pat. No. 4,484,801 to Cox: and U.S. Pat. 4,566,763 to Greguss. Each of these has its own advantages and disadvantages.
In particular, the Greguss patent proposes a panoramic block such that light entering it undergoes a total of two refractions and two reflections before exiting. Both reflective surfaces are paraboloidal in shape for achieving, according to the specification, nearly faultless imagery. Each of these surfaces can be replaced, according to the specification, with a surface having a radius of the "best fit" sphere for a still acceptable image quality.
While the general concept of the Greguss'0 patent is useful, it has been found by analyzing his system in detail that it is faulty in certain aspects. The utilization of paraboloidal reflective surfaces and a telecentric exit pupil actually compromise the performance of the design of the overall system rather than enhancing it. It can be proven that the Greguss system would work better with spherical reflective surfaces than with paraboloidal ones.
Further, the Greguss patent does not address any relay optics or relay lens in detail. Such lens, or a relay system following the primary component (panoramic block) is not only important but necessary for transferring the intermediate image, formed somewhere in the primary block, further on to produce a real accessible image on, for example, a CCD camera.